1. The Field of the Invention
The invention generally relates to interventional cardiology. More specifically, the invention relates to procedures performed within a body lumen. The invention further relates to systems for providing embolic protection during procedures performed in a body lumen.
2. The Relevant Technology
Human blood vessels often become blocked with deposits such as plaque, thrombi, and other materials. If the blockage occurs at a critical place in the vessel, serious and permanent injury, or even death, can occur. To prevent these results, medical intervention is performed to clear the occluded vessel.
Several procedures are currently used to open stenosed or occluded blood vessels. Balloon angioplasty is a well known method for opening occluded blood vessels which involves inserting a balloon-tipped catheter into an occluded region of a blood vessel. After being inserted into the blood vessel, the balloon is inflated and the stenosed region of the blood vessel is dilated, thereby increasing the intraluminal diameter.
Another technique for opening stenosed blood vessels is atherectomy. Atherectomy refers to a procedure which employs a rotating blade to shave plaque from an arterial wall. A catheter including a rotating blade or cutter is inserted into the blood vessel. Located at the tip of the catheter is an aperture and, on the opposite side of the catheter tip from the aperture, a balloon. The tip is placed in close proximity to the fatty material and the balloon is inflated, thereby forcing the aperture into contact with the fatty material. When the blade or cutter is rotated, the fatty material is shaved off and retained within the interior lumen of the catheter. This process is then repeated until sufficient fatty material has been removed from the wall of the blood vessel.
An additional procedure for opening stenosed or occluded blood vessels includes stent introduction. A stent typically includes a cylindrical tube or mesh sleeve made from materials such as NiTiNOL or stainless steel. The characteristics of the material permit the diameter of the device to expand radially while still providing sufficient rigidity such that the stent maintains its shape once it has been enlarged to the desired size.
Many medical devices are used in placing a stent in a body lumen. After access to the arterial system has been established, a guide catheter is inserted into the artery and the tip of the catheter is positioned proximal to the occluded region of the blood vessel. A guide catheter allows other devices to be rapidly delivered to the stenosed region without being carefully guided from the point of access to the arterial system to the point of intervention. A small diameter guide wire is inserted through the catheter and guided to a point proximate the stenosed region. After the guidewire has been successfully put in place, the stent is attached to a delivery device and installed over the guide wire. When correctly placed, the stent will be deployed in a manner which will maintain the blood vessel open at that point.
Many different types of stents are used in intravenous procedures. Often a system requires a stent to be deployed or expanded from a compressed state by a balloon to which the stent is attached. When the balloon is inflated not only is the stenosed region opened, the stent is also embedded into the inner region of the blood vessel at that point.
The guidewire not only facilitates delivery of the stent to the stenosed region, it also serves the purpose of providing a delivery mechanism for all other devices which may be used in the procedure. Devices which may be needed in the procedure contain an inner lumen through which the guidewire is inserted. The device then slides along the guidewire into the body of the patient, with the guidewire guiding the device to the desired location. The process of sliding devices over the guidewire for delivery into the patient is commonly known as an exchange. The ability to perform an exchange reduces the invasive nature of the interventional procedure.
When interventional procedures are performed with occluded blood vessels, particles are released from the vessel wall. These embolic pieces can then flow downstream potentially causing adverse effects. To prevent the dangers associated with embolic particles flowing through the blood stream, devices are emerging which are designed to catch or filter such particles. The particles are then aspirated out of the blood stream before they can flow downstream.
Filter and trapping systems designed to capture particulate matter released during intravenous procedures include many forms. Trapping devices are often structured as an umbrella-like device designed to catch emboli as they are released from the vessel wall during an atherectomy or angioplasty procedure. Filter devices are also designed to catch released embolic material and can be either permanently or temporarily deployed in the blood vessel.
Both permanent and temporary filtering devices can present serious difficulties. Accurate deployment of permanent filtering devices is difficult and incorrect placement can limit filtering capabilities. Furthermore, permanent devices have been designed to filter large blood clots and have proven ineffective for trapping smaller emboli. In certain cases a permanent filter may accumulate too much clot and block of the area of the blood vessel in which it rests. In addition, permanent filters are often secured to the vessel wall by anchoring hooks which, with time, may cause the vessel wall to rupture due to erosion. Temporary filters, while circumventing many of the problems present in permanent devices, also present certain difficulties. Even if temporary filters succeed in capturing emboli from within the blood vessel it is difficult to remove the filter without redepositing the emboli into the blood stream.
The device and methods described herein are designed to overcome these and other deficiencies in current devices and to allow safer and better protection for the patient from particulates which may be released into the blood stream during an intravenous procedure.